Re: [boost] variant - off topic

Subject: Re: [boost] variant - off topic
From: degski (degski_at_[hidden])
Date: 2019-04-08 05:59:44

On Sun, 7 Apr 2019 at 18:44, Robert Ramey via Boost <boost_at_[hidden]>
wrote:

> template<T ...>
> struct safe_variant : public std::variant<T...> {
>      // for each T static assert that is_trivially_constructible<T> == true
> };
>
> Which gets trickier.  But would be cool if someone wanted to make this.
>

#include <type_traits>
#include <variant>

struct Foo {
    Foo ( ) = delete;
};

template<typename... Args>
struct safe_variant : public std::variant<Args...> {
    static_assert (
std::conjunction<std::is_trivially_constructible<Args>...>::value, "is not
trivially constructible" );
};

int main ( ) {

    safe_variant<int, double, bool> sv1; // compiles
    // safe_variant<int, double, bool, Foo> sv2; // does not compile
}

Unless I mis-understand what you mean, this does the trick.

degski
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